21388897 has 2 divisors, whose sum is σ = 21388898. Its totient is φ = 21388896.

The previous prime is 21388891. The next prime is 21388943. The reversal of 21388897 is 79888312.

It is an a-pointer prime, because the next prime (21388943) can be obtained adding 21388897 to its sum of digits (46).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14814801 + 6574096 = 3849^2 + 2564^2 .

It is a cyclic number.

It is not a de Polignac number, because 21388897 - 2⁷ = 21388769 is a prime.

It is not a weakly prime, because it can be changed into another prime (21388891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10694448 + 10694449.

It is an arithmetic number, because the mean of its divisors is an integer number (10694449).

Almost surely, 2^21388897 is an apocalyptic number.

It is an amenable number.

21388897 is a deficient number, since it is larger than the sum of its proper divisors (1).

21388897 is an equidigital number, since it uses as much as digits as its factorization.

21388897 is an evil number, because the sum of its binary digits is even.

The product of its digits is 193536, while the sum is 46.

The square root of 21388897 is about 4624.8131854162. The cubic root of 21388897 is about 277.5850865885.

The spelling of 21388897 in words is "twenty-one million, three hundred eighty-eight thousand, eight hundred ninety-seven".